Night Shift by Charlaine Harris

The residents of Midnight, Texas have a new problem, people are coming there to kill themselves.  Strange is putting it mildly.  Then it gets worse, Fiji's sister shows up and throws an even bigger wrench into the fray.
Fast paced, enough humor to keep you going and more than enough questions to keep the pages turning.  Highly recommend it but best if you read the other two first.